Due to sweating and contaminants in the air, it is easy for bacteria to grow on those textile products that come into contact with human body, such as clothings, towels and bedclothes. As a result, such bacterial growth causes dermatopathy and unpleasant phenomenon due to the offensive odor generated by the decomposed matters of bacteria, as well as alteration, discoloration and deterioration of the fibers. Particularly, since synthetic fibers absorbs only a small amount of sweat, there is a problem that microorganisms are likely to grow on such textile product due to the sweat deposited when the textile product is worn.
Partly because of the recent increase in the recognition and orientation toward hygiene among consumers in general, a number of methods for imparting antimicrobial properties to a textile product have been devised. Examples of such methods include one in which the spinning solution is kneaded with an antimicrobial agent and spun into fibers and one in which fibers are impregnated with a solution of antimicrobial agent.
As the antimicrobial agent used in such the above-mentioned methods for imparting antimicrobial properties to a textile product, cationic polypeptides such as ϵ-polylysine and protamines, which are also used as food additives, are highly safe and useful. It is noted here that the term “protamine” collectively refers to histone-like peptides originated from fish sperm nucleus, and specifically, it is a peptide having an arginine-rich structure.
Examples where ϵ-polylysine was used so far include those in which a spinning solution, such as polypropylene or polyethylene, was kneaded with ϵ-polylysine and spun into fibers (Japanese Unexamined Patent Application Publication No. H10-310935, Japanese Patent No. 3596147); one in which ϵ-polylysine was graft-polymerized into a macromolecule (Japanese Unexamined Patent Application Publication No. 2008-303287); and the method in which fibers are impregnated with a solution containing ϵ-polylysine solution and other components (Japanese Unexamined Patent Application Publication No. 2005-314823, Japanese Patent No. 3883763, Japanese Unexamined Patent Application Publication No. H11-61639). In addition, examples where protamine was used include the method in which protamine is applied as an antifungal agent and allowed to adhere to a nonwoven fabric (Japanese Unexamined Patent Application Publication No. 2003-166155).
Among these methods, since the bacteriostatically treating method in which an antibacterial agent is attached to fibers by impregnation or application is particularly simple, it is desired to generalize the use thereof.
However, in the treatment conditions of the aforementioned prior arts, the bacteriostatic effect cannot be maintained as the antibacterial agent is removed during washing; thus, components other than cationic polypeptide are allowed to exist during the treatment. That is, there has not been achieved a method for bacteriostatically treating a textile product in such a manner that the bacteriostatic effect of the antibacterial agent is not reduced and thus retained even after the textile product is washed for a plurality of times.